The present invention relates to a mechanical seal and, more particularly, to a shaft-sealing device for a pump.
It is usual to mount a mechanical seal in a pump for sealing between a pump housing of the pump and a rotary shaft. A typical mechanical seat generally includes a stationary ring secured in the pump housing and a rotary ring moveably mounted around the rotary shaft or a shaft sleeve and biased by springs toward the stationary ring to provide sealing engagement therebetween, thereby preventing a transported pump fluid in the pump housing from leaking from a relatively moveable interface between the stationary and rotary rings to the environment. In such a mechanical seal, the stationary and rotary rings will wear and generate considerable heat during relatively rotational operation at the sealing interface due to direct metal-to-metal contact therebetween. To reduce the wear and heat at the sealing interface, an additional cooling and/or lubricating device is often required.
Taiwanese Patent Publication No. 300603 discloses a shaft-sealing device including a stationary ring mounted around a rotary shaft and secured in a pump housing, and a rotary ring is moveably mounted around the rotary shaft to rotate therewith and biased toward the stationary ring to provide sealing engagement therebetween. A coolant pumped by an external source circulates in a shaft-sealing chamber in the pump housing through conduits connected to an inlet and an outlet in the pump housing to cool and/or lubricate the sealing surfaces. Further, the rotary ring is provided with a plurality of slots annularly spaced from one another in an outer circumference thereof to assist in stirring the coolant in the shaft-sealing chamber when rotating with the rotary shaft. However, the cooling effect of the coolant in the shaft-sealing chamber is not sufficient, as discharge of the coolant through the outlet is relatively slow, resulting in a poor heat exchange. Further, the rotary ring is generally made of wear-resisting carbide, and the outer circumference of the rotary ring provided with slots is disposed close to an inner wall of the pump housing for a greater stirring area. As a result, the rotary ring may contact the inner wall of the pump housing due to accidents such as shock, causing flare or electric potential difference and thus leading to hazards of breakdown.
Thus, a need exists for a mechanical seal that can improve the cooling effect of the coolant and assure safe operation while having a simplified structure.